As a method of checking whether the cause of ischemia of a patient suffering ischemic heart disease is a stenosis, a method using a fractional flow reserve (FFR) index has been developed. The clinical effectiveness of FFR has been confirmed by randomized clinical trials.
To obtain FFR, it is necessary to insert a pressure sensor-equipped wire (pressure wire) into a blood vessel and measure a stenosed blood vessel upstream pressure Pa and stenosed blood vessel downstream pressure Pd, as shown in FIG. 6.